Technical Field
The present disclosure generally relates to microelectronic sensors, and in particular, to consumable biosensors that are flexible and can contain a fluid for electrochemical monitoring.
Description of the Related Art
Biosensor strips are used to monitor blood glucose levels by millions of patients who suffer from diabetes. With reference to FIG. 1, a typical home monitoring apparatus 80 includes a conventional disposable strip biosensor 82 and a portable electronic monitor 83. A blood sample is applied to the biosensor 82, and the strip is inserted into the portable electronic monitor 83. A conventional biosensor 82 is made of a semi-rigid backing material 84 approximately an inch long, impregnated with an electrolytic chemical reagent 86 at one end and printed with electrodes 88 at the other end. The patient pricks a fingertip, applies a drop of blood 89 to the reagent 86, and inserts the electrodes 88 into the portable electronic monitor 83. The electrolytic chemical reagent 86 conducts a current that is proportional to an amount of glucose in the blood. Current flow conducted via the electrodes 88 in the biosensor 82 closes a circuit when the biosensor 82 is inserted into the portable electronic monitor 83. The current in the circuit can then be measured by the portable electronic monitor 83. The portable electronic monitor 83 is configured with software that converts the current measurement into a numerical value that represents the blood glucose level. The portable electronic monitor 83 then provides a digital readout of the numerical value and stores the numerical value as blood glucose data in an electronic memory. By either recording or downloading the blood glucose data, the patient can track blood glucose values over time to adjust insulin dosage.
A drawback for manufacturers is that the chemical reagent, which is typically in liquid form, must be cross-linked into a solid form that is suitable for incorporation into the biosensor strip. Furthermore, techniques used to fabricate the electrodes, the chemical reagent, and the packaging are specific to three different industries, namely the semiconductor, bio-chemistry, and packaging industries, respectively. Thus, the current sensors and manufacturing process tend to be costly, overly complex, and disjointed, which results in a higher product cost to consumers.
In-situ monitoring systems offer many advantages over the patient-administered home monitoring system described above. In one type of in-situ monitoring system, a transdermal patch is used to secure a blood sampling needle and a drug delivery needle to a patient's skin. Blood glucose can be detected by a circuit within the patch, and the data can be wirelessly relayed by an antenna in the patch for remote processing and dose calculation. Likewise, a wireless signal containing the determined dosage information can be received by an antenna in the patch and used to electronically control insulin delivery. By automating the monitoring and dosing functions, such a system eliminates the need for patients to handle fluid chemical reagent strips or syringes of insulin. However, although the transdermal patch is generally more accurate and more convenient than the home monitoring system, it is still cumbersome. For example, the patient must apply the transdermal patch, wear the patch at all times, and periodically re-load the patch with insulin. Because it is not fully automated, the transdermal patch still incurs opportunities for error in dosing.
There also exist environmental micro-sensors, such as temperature and humidity sensors, that monitor environmental conditions by exposing dielectric films that are sensitive to ambient conditions. Embodiments of such sensors are described in U.S. patent application Ser. Nos. 13/853,732 and 13/315,477, for example. Some environmental sensors are integrated with chemical sensors, as disclosed in U.S. Patent Application Publication No. US 2012/0168882. However, existing micro-sensors are typically tailored for either a bio-medical or an environmental application, and are generally not interchangeable.